We are requesting funds for the purchase a new API 5000 tandem quadrupole LC- MS/MS system, with turboionspray and atmospheric-pressure chemical ionization ion sources, manufactured by Applied Biosystems of Foster City, CA. The device will be used by the eight participating faculty, as well as other scientists in the MIT community, to quantify and characterize biological and synthetic molecules in studies affecting at least eighteen NIH-funded research projects. Our current single triple quadrupole mass spectrometer (API 3000) in the Center for Environmental Health Sciences (CEHS) is becoming overwhelmed by sharply increasing demand for LC-MS/MS analyses requiring greater sensitivity, mainly in the area of biomarker quantification. The co-applicants all have demonstrated needs for the API 5000 system for research projects funded by the NIH: Peter Dedon, John Essigmann, James Fox, Alan Grodzinsky, Leona Samson, David Schauer, Steven Tannenbaum, and John Wishnok. The projects that would benefit from the API 5000 range widely from proteomic analyses of cellular responses to infectious agents and mechanical stresses; anticancer drug design; drug metabolism in bioengineered liver tissue; to DNA, RNA, protein and lipid biomarkers of oxidative and nitrosative stress arising at sites of inflammation in humans. In all cases, the goal is to take advantage of the sensitivity and chemical specificity of the API 5000 triple quadrupole mass spectrometer system to rigorously quantify synthetic and biological molecules at the relatively low levels that occur in diseased and healthy human tissues, with sensitivities in the range of attomoles to femtomoles. No other system meets these demands. The public health relevance of the studies that would be supported by the API 5000 lies in their goals to develop sensitive methods to quantify molecules involved in both the therapy and the pathophysiological basis for human diseases. Sensitive measuring devices such as the API 5000 are crucial to the objective of moving NIH-sponsored research into humans - from bench to bedside. [unreadable] [unreadable] [unreadable]